The absorption principle of microperforation has been known and described just for sound insulation in numerous printed documents (cf., for example, WO 01/12470 A1). In principle, it is the application of parallel Helmholtz resonators that may be arranged in front of a fibrous or porous absorber material. The principle of such an arrangement, so-called perforated absorbers, has long been known and is also described in some detail in the technical literature.
On the other hand, needle-punching machines for needle-punching fibers to a needle-punched non-woven have been known independently thereof.
From DE 33 21 094 C2, a textile material for the preparation of quilts, clothing, pillows, cushions or carpets has been known in which an aluminum layer is applied to the textile material and treated with a needle-punching machine. This aluminum layer is applied by vapor deposition, for example, and therefore is not self-supporting.
DE 22 53 990 describes the line-shaped perforation of a variety of materials.
DE 42 26 872 A1 describes the perforation of wood.
DE 26 23 851 A1 describes the perforation of a plastic sheet.
DE 697 17 789 T2 describes a material plate of metal with microslits.
DE 102 53 830 A1 describes the perforation of aluminum foil by means of a perforation knife with teeth.
DE 24 10 060 A1 describes a device for perforating sheets of plastic, artificial leather, paper or composite material.
DE 197 51 983 A1 describes the needle perforation of plastic sheets.
DE 2203 16 050 U1 describes the microperforation of aluminum foils by means of a porcupine roller.
The perforated foils known to date for sound insulation have the drawback that either they are very complicated to prepare, or the foil must be relatively thick in order that the perforation channels have a length sufficient for sound insulation.